HPLC/MS ANALYSIS OF SOLANINE IN PHYSALIS ALKEKENGI AND SOLANUM DULCAMARA

172 HPLC/MS ANALYSIS OF SOLANINE IN PHYSALIS ALKEKENGI AND SOLANUM DULCAMARA CLAUDIA BUTNARU 1*, LAURIAN VLASE 2, DOINA LAZĂR 1, LUMINIŢA AGOROAEI 1, MIHAI IOAN LAZĂR 1 1 University of Medicine and Pharmacy Gr. T. Popa, Faculty of Pharmacy, 16 University Street, 700115, Iaşi, Romania 2 University of Medicine and Pharmacy Iuliu Haţieganu, Faculty of Pharmacy, 13 Emil Isac, 400023, Cluj-Napoca, Romania * corresponding author: butclaudia@yahoo.com Abstract We developed a HPLC/MS method for the identification and determination of solanine in plants. This method was applied for samples of Solanum dulcamara (from Iaşi and Vânători Neamţ areas in Romania) and Physalis alkekengi (from Bucium and Breazu, Iaşi, Romania) during August-September 2009. Isolation of solanine was performed by extraction with a mixture consisting of water/methanol/acetic acid 49/49/2 (v/v/v) in an ultrasonic bath. Solanine was determined in concentrations ranging between 0.7963 µg/g vegetal product (leaves, Zimbru, Romania) and 4.2166 µg/g (leaves, Iaşi area) in Solanum dulcamara and between 0.092 µg/g (fruits, Bucium) and 0.2818 µg/g (stems, Bucium) in Physalis alkekengi. For Physalis alkekengi, in leaves (sample from Bucium) roots and fruits (sample from Breazu) the concentration values of solanine were below the detection limit. The mean concentration of solanine was 21.67 times greater in samples of Solanum dulcamara than in Physalis alkekengi. For Solanum dulcamara, the highest concentration of solanine was recorded in stems. Rezumat Lucrarea prezintă o nouă metodă HPLC/MS pentru identificarea şi dozarea solaninei din plante. Prin această metodă s-a analizat solanina din părţile plantelor Solanum dulcamara (recoltată din zona Iaşi şi Vânători Neamţ) şi Physalis alkekengi (recoltată din Bucium şi Breazu, Iaşi) recoltate în perioada august-septembrie 2009. Izolarea solaninei s-a realizat prin extracţie cu un amestec de apă/metanol/acid acetic 49/49/2 (v/v/v) în baia cu ultrasunete. Solanina a fost determinată în concentraţii de 0,7963 µg/g produs vegetal (frunze, Zimbru) şi 4,2166 µg/g produs vegetal (frunze, zona Iaşi) în Solanum dulcamara şi între 0,092 µg/g produs vegetal (fructe, Bucium) şi 0,2818 µg/g produs vegetal (tulpini, Bucium) în Physalis alkekengi. Pentru Physalis alkekengi probele de frunze din Breazu şi cele de rădăcini şi fructe din Breazu au prezentat valori sub limita de detecţie. Valoarea medie a concentraţiei solaninei în probele de Solanum dulcamara a fost de 21,67 ori mai mare decât cea din probele de Physalis alkekengi. Pentru Solanum dulcamara, cele mai mari concentraţii s-au determinat în tulpinile plantelor. Keywords: solanine, Solanum dulcamara, Physalis alkekengi, HPLC/MS

173 Introduction Solanine is a glycoalkaloid toxine in species of the Solanaceae family. It can occur naturally in any part of the plant, including the leaves, fruits and tubers. Solanine has fungicidal and pesticidal properties and it is one of the plant s natural defenses. Solanine was first isolated in 1820 by Desfosses from the berries of the European black nightshade (Solanum nigrum), after which it was named. This toxin has neurological and gastrointestinal effects. Historically, solanine was used in the treatment of epilepsy and asthma, in controlled doses. This practice is no longer common. Solanine from unripe fruits of Solanum dulcamara has antimicrobial activity by inhibiting the growth of Escherichia coli and Staphylococcus aureus [5,7]. Recent studies demonstrated the antiproliferative activities of solanine against human colon (HT29) and liver (HepG2) cancer cells. The effectiveness against the liver cells was greater than against the colon cells. Other studies confirmed the anticarcinogenic effects of solanine against human cervical, liver, lymphoma and stomach cancer cells [1, 4, 6]. The most analyzed solanine is that from potato. There are few studies on solanine from other plants of the Solanaceae family. This compound is a potential treatment for infections and cancer, this is why, we should explore other sources [2,3]. Within phytochemical research of Physalis alkekengi and Solanum dulcamara, we determined solanine qualitatively and quantitatively by highperformance liquid chromatography tandem mass spectrometry (HPLC/MS) [8]. Materials and methods Plant samples were harvested around Iaşi, Romania as follows: Solanum dulcamara: August-September 2009 Iaşi and Vânători Neamţ area. Physalis alkekengi: August-September 2009 Bucium and Breazu, Iaşi. At 100 mg powder of plant product 5 ml water/methanol/acetic acid 49/49/2 (v/v/v) was added and was let at rest for 24 hours in the dark at room temperature. After that the samples were placed in an ultrasonic bath for 30 minutes. 1 ml of solution was introduced into an Eppendorf tube and was centrifuged for 5 minutes at 12,000 rpm. 200 µl were further used for the HPLC/MS analysis. A standard of solanine (Fluka) was used for the quantitative determination (figure 1).

174 The HPLC tandem mass spectrometer equipment was composed of HP 1100 Series binary pump, autosampler and thermostat, mass spectrophotometer Agilent Ion Trap 1100 SL. The HPLC column was Zorbax SB-C18 100 mm x 3.0 mm i.d., 3.5 µm. The mobile phase was a mixture of 0.1% formic acid and methanol 75/25 (v/v), isocratic elution, flow rate: 1 ml/min, temperature: 40 C. The MS detection was performed by isolation and ion fragmentation with m/z 869, corresponding to protonated solanine, then ions with m/z 706.4 and 722.4 were monitored by MS/MS spectrum of the analyte. Results and discussion Figure 1 Chemical structure of solanine HPLC/MS analysis of solanine standard Full-scan spectrum of a solution with solanine is presented in figure 2. According to the molecular mass of solanine (M=868.0) and in accordance with the positive ionization mode, the expected ion would be the ion with m/z 869.0, adequate for the protonated molecule. Intens. x10 6 3 869 +MS 2 1 0 100 200 300 400 500 600 700 800 900 m/z Figure 2 Full-scan spectrum of solanine in mobile phase

175 In order to increase the selectivity of the HPLC/MS method, characteristic ion of solanine fragmentation was achieved and MS spectrum was recorded (figure 3). Intens. x10 5 706.4 +MS2(869) 3 2 398.3 1 868.5 0 560.3 400 450 500 550 600 650 700 750 800 850 m/z Figure 3 MS/MS spectrum of solanine in mobile phase Note that by fragmentation, solanine is split into four main fragments with m/z 398, 560, 706 and 722. The most intense ions with m/z 706 and 722 were chosen for quantification. Figure 4 shows a chromatogram of solanine after MS/MS detection. Intens. x10 4 1.25 1.00 0.75 0.50 0.25 0.00 0.0 0.5 1.0 1.5 2.0 2.5 Time [min] Figure 4 The solanine chromatogram by MS/MS detection, at limit of the method quantification The calibration curve of solanine was performed in the concentration range 6-180 ng/ml.

176 HPLC/MS analysis of solanine from Physalis alkekengi and Solanum dulcamara The results are expressed in µg solanine/g vegetal product and are presented in tables I (for Solanum dulcamara) and II (for Physalis alkekengi). Table I Solanine concentration in Solanum dulcamara Part of plant Location Solanine leaves Iaşi 4.2166 leaves Zimbru 0.7963 stems UMF 3.8303 stems Zimbru 3.2025 roots UMF 1.6007 roots Zimbru 1.5116 fruits UMF 1.3639 fruits Zimbru 1.5501 Maximum 4.2166 Mean 2.2590 Minimum 0.7963 For Solanum dulcamara (figure 5), the highest concentration value of solanine was recorded in the stems (mean 3.51 µg/g vegetal product); quantities are similar in fruits (mean 1.45 µg/g vegetal product) and roots (mean 1.55 µg/g vegetal product). Figure 5 The variation of mean values of solanine concentration in Solanum dulcamara

177 Table II Solanine concentration in Physalis alkekengi Part of plant Location Solanine leaves Bucium 0.0000 leaves Breazu 0.1442 stems Bucium 0.2818 stems Breazu 0.0920 roots Bucium 0.2233 roots Breazu 0.0000 fruits Bucium 0.0926 fruits Breazu 0.0000 Maximum 0.2818 Mean 0.1042 Minimum 0.0920 For Physalis alkekengi, in leaves (sample from Bucium, Romania) roots and fruits (sample from Breazu, Romania) concentration of solanine was below the limit of detection. For Physalis alkekengi, the highest concentration of solanine was recorded in stems (mean 0.18 µg/g vegetal product), same as Solanum dulcamara, but the quantities are much lower than those obtained for Solanum dulcamara. The mean concentration of solanine is 21.67 times greater in samples of Solanum dulcamara than in Physalis alkekengi and the minimum detectable quantity was 8.65 times lower in samples of Physalis alkekengi than the minimum value detected in Solanum dulcamara. The concentration variations in all samples of Solanum dulcamara are shown comparatively to those of Physalis alkekengi in figure 6. 4.5000 4.0000 3.5000 3.0000 micrograms/g 2.5000 2.0000 Solanum dulcamara Physalis alkekengi 1.5000 1.0000 0.5000 0.0000 1 2 3 4 5 6 7 8 Samples Figure 6 Solanine concentrations in Solanum dulcamara compared to Physalis alkekengi

178 Conclusions We developed a HPLC/MS method for the identification and determination of solanine in plants. This method was applied for two plants: Physalis alkekengi and Solanum dulcamara. Solanine was determined in concentrations ranging between 0.7963 and 4.2166 µg/g vegetal product in Solanum dulcamara and between 0.092 and 0.2818 µg/g vegetal product in Physalis alkekengi. For Physalis alkekengi, in leaves (sample from Bucium, Romania), roots and fruits (sample from Breazu, Romania) the concentration of solanine was below the limit of detection. The mean concentration of solanine was 21.67 times greater in samples of Solanum dulcamara than in Physalis alkekengi. For Solanum dulcamara, the highest concentration of solanine was recorded in stems. References 1. Friedman M., Lee K.R., Kim H.J., Lee I.S., Kozukue N., Anticarcinogenic effects of glycoalkaloids from potatoes against human cervical, liver, lymphoma, and stomach cancer cells. J Agric Food Chem, 2005, 53(15), 6162-6169 2. Friedman M., Roitman J.N., Kozukue N., Glycoalkaloid and calystegine contents of eight potato cultivars. J Agric Food Chem, 2003, 51(10), 2964-2973 3. Jensen P.H., Juhler R.H., Nielsen N.J., Hansen T.H., Strobel B.W., Jacobsen O.S., Nielsen J., Hansen H.C., Potato glycoalkaloids in soil-optimizing liquid chromatography-time-offlight mass spectrometry for quantitative studies. J Chromatogr A, 2008, 1182(1), 65-71 4. Ji Y.B., Gao S.Y., Ji C.F., Zou X., Induction of apoptosis in HepG2 cells by solanine and Bcl-2 protein. J Ethnopharmacol, 2008, 115(2), 194-202 5. Kumar P., Sharma B., Bakshi N., Biological activity of alkaloids from Solanum dulcamara. Nat Prod Res, 2009, 23(8), 719-723 6. Lee K.R., Kozukue N., Han J.S., Park J.H., Chang E.Y., Baek E.J., Chang J.S., Friedman M., Glycoalkaloids and metabolites inhibits the growth of human colon (HT29) and liver (HepG2) cancer cells. J Agric Food Chem, 2004, 52(10), 2832-2839 7. Sotelo A., Serrano B., High-performance liquid chromatographic determination of the glycoalkaloids alpha-solanine and alpha-chaconine in 12 commercial varieties of Mexican potato. J Agric Food Chem, 2000, 48(6), 2472-2475 8. Bucur L., Vlase L., Istudor V., Popescu A., HPLC-MS analysis of the plyphenols in two soft extracts of Elaeagnus angustifolia L. Note 2. Soft extract of young branches analysis, Farmacia, 2009, 57(6), 736-742. Manuscript received: September 8 th 2010